1. Field of the Invention
The invention relates to a non-volatile memory (NVM) and a manufacturing method thereof. More particularly, the invention relates to a non-volatile memory capable of preventing second bit effect and program disturbance and a manufacturing method thereof.
2. Description of Related Art
Non-volatile memory has the advantage of saving the stored data after the power is turned off. Thus, this type of memory is adopted in many electronic products to maintain the operation of electronic products when turned on.
Nitride read only memory (ROM) is a common non-volatile memory nowadays. In a memory cell of a nitride ROM, a charge trapping structure constituted by a nitride layer can store two-bit data. Generally, two-bit data can be stored in the left side (that is, left bit) and the right side (that is, right bit) of the charge trapping structure respectively.
However, two bit effect is present in the nitride ROM. In other words, a read operation on the left bit is affected by the right bit, or a read operation on the right bit is affected by the left bit. Also, with the reduction in the size of memory, the length of the channel in the memory cell is reduced as well, such that the second bit effect is more severe, thereby affecting operation window and device performance.
Further, as the size of the memory decreases gradually, the distance between the memory cells decreases as well. Consequently, program disturbance easily results when adjacent memory cells undergo a program operation.